/Engine/Plugins/FX/Niagara/Source/NiagaraEditor/Public/ViewModels/NiagaraSystemViewModel.h
typedef TMulticastDelegate_ThreeParams< void, const [FNiagaraVariableBase](API\Plugins\Niagara\FNiagaraVariableBase) &, const [FNiagaraVariableBase](API\Plugins\Niagara\FNiagaraVariableBase) &, [UNiagaraEmitter](API\Plugins\Niagara\UNiagaraEmitter) * > FOnExternalRenameParameter